Ionization gauge regulation



July 22, 1952 H. G. NEIL I IONIZATION GAUGE REGULATON Filed Aug. 16, 1944 IIIII- ahw.

IL Il INVENTOR. i mgh ain/ea VBY lbroadly claimed in an application Ser. v-546,902, led vJuly 27,1944, by Stephen M. Mac- Patentecl July 22, 1952 UNITED STATES PATENT oFFlcEv IONIZATION GAUGE REGULATION Hugh G. Neil, Oak Ridge, Tenn., assignor, by mesne assignments, to' the United States of America as represented by the United States Atomic Energy Commission Application August 1G, 1944, Serial No. 549,773

5 Claims.

"is the provision of a circuit which furnishes improved regulation which is very rstable and which does not require adjustment.

Other objects and advantages of the invention will become apparent from the following description when read in connection with the `accomrpanying drawing, the single gure of which illustrates 'schematically the preferred embodiment of the invention.

The operation of an ion vacuum gauge so that the electron current required to produce a pre- "determined ionization is an indication of the pressure of the gas being ionized is disclosed and No.

Neille, now'Patent No. 2,537,775.

Referring to the drawing, a gas discharge tube I having a filament I I, a grid I2 and a plate I3 is connected and operated so that an electronicI discharge from the filament II ionizes the gas within' the tube I0 to produce a predetermined ion current to the plate I3. This ion current is maintained constant under varying pressure by -varying the electronic discharge which is collected by the grid I2 and measured as an indicationiof pressure. For this purpose the lament IIr is connected to be adjustably energized from a. suitable power source I4' through a transformer I5 and a saturable reactor IB havingv a D. C. winding I1. Also connected to the power source I4 is a conventional power supply including a full wave rectifier I8 the output of ywhich is filtered and impressedacross a voltage divider comprising resistances I9, 20, and 2I in series,l

this-voltage divider having associated therewith in Vshunt relation two voltageregulating tubes 22 and 23 and a resistance 24. The filament IIA of the ion tube I0 is given a potential ofA 45 vvolts above ground by connecting it between a voltage regulating tube 25 and a resistance 26 forming a, series shunt across the regulating tube 22. Thegrid I2 of the tube I0 is maintained positive with respect to the lament I I by being connected between resistances' I9 vand 20 `in. the

vare emitted and ionization occurs.

2 voltage divider. The plate. I3 of the tube I0 is maintained negative with respect to the iilament I I as will later be' described. Thus the filament II is 'negative with respect to the grid I2 and positive with respect to the plate I3 so that the grid I 2Y functions as an anode to collect "electrons and the plate I3 collects positive ions.

The circuit for regulating ion current collected by the plate I3 comprises a duotriode tube 21, preferably type 6SC7, having a cathode 28 common to two grid-plate combinations 29, 30 and 3I, 32, respectively, connected so that the plate current through the plate 3!! and the cathode 28 flows to ground through a resistance 33 in the common lead to the cathode 28 to hold the cathode 28 at approximately 26 volts. The plate 30 is connected to the positive side of the voltage regulating tube 23 through a resistance 34 andthe grid 29 is connected to a regulated 25volts between resistances 20 and 2I.Y The other triode -in the tube 21 has its grid 3| connected to the plate I3 of the tube Ithrough a resistance 35 and senses variations in the ion current collected by the plate I3 asa voltage drop across a resistance'36 provided in the ion current path, and has its plate 32 connected through a resistance 31 to the 300 volt side of the voltage regulator tube 23. It is to be understood that the numerical values and various circuit constants mentioned are illustrative of a circuit adapted to regulate at a potential of 24.6 volts on the grid 3| and the plate I3 but are not limiting.

With no ionization in the tube I0 there will be no voltage drop across the resistance 36, the grid 3l will be at zero voltage which is 26 volts nega- -tive with respect to its cathode 28 and its plate ply through the D. C. winding I1 of the saturable reactor I6. The tube 39 which may be type 68H7, isccnducting, and the ow of its plate currentthrough the winding I1 brings about an .increased voltage Yo n the transformer I5 so that the vfilament I Iof the tube vIII is heated; electrons The ions collected by theplate I3 furnish av current through the resistance 36 which increases until the voltage drop becomes 24.6 volts at which time the current through the resistance 31 has lowered the potential of the plate 32, and hence the grid 38, so that less plate current flows through the tube 39 andthe winding I7. This increases the impedance of the reactor I6 which brings about a reduction in the temperature of the tube lament I I to the point Where just enough electrons are emitted to produce ionization sucient to provide a voltage drop of 24.6 volts acrossthe resistance-Sii. The electron emissionrequired for this purpose will differ for different pressures in the tube I and therefore, a meter 42 included in the circuit of the grid (anode) I2 Will give a reading indicative of thepressure in the tube I0.

Another range of plate .current in the tube i6 may be provided by using a1 different: value. for the resistance 36. This `may conveniently tbe done by providing an additional resistance 43 and a selector switch 44. Y

It will be noted that the potential difference between the lament II and the grid [2 'of' ther tube I9 is held constant by the voltage regulator ltube and thev potential difference'betweenthe 'lament I'I and'theplate'IS Vi's'held constantby "the-drop lacross the resistance '25A whenthe ion currentithrough the gaugeY tuberi 9 IisV constantL at 'its regulated value.

The .circuit of the :present invention* functions to regulatethe supply' of VenergyV to 'the filament of aV vacuumgauge vso'that :a'constantspace current 'is' maintained' therein under :varyingconditions of pressure. By means of the invention `stable regulation isObtaine'd without fthe need Y*.toriadjustrnent.

'While a specific circuit arrangement has lbeen Adescribed Yto* illustrater the"in`vention, vit will be evident vthat modifications may :be Inade'with- YVout departing from the scope ofrthe linvention Yas fset oorth Vin the. appended-claims.

.I'clairnrV i1. In an ion Avacuum :gauge circuit Viin -rwhich the-ion current 4'is held constant and the electron fcurrent indicates pressure; a-pair of triodeshaving electrically connected cathodes yconnected. through acommon resistance'ftoJacommon fixed potential, means forfsupplying-"oneof the triode's with xed voltages on'its :plateandgrid a connection from 'the grid Vof the other'triodeto vthe ion collecting' plate of thesionvacu'um gauge, a

'iilament current control circuitfor saidiion gauge `tain constantthe ratei of ionization of'a gas under Varying conditions v'oflpre'ssure-cornprisi'n'g a duotriode discharge device having tw'o `s'etslof `control and output electrodes and a common-fcathode, vmeans for applyingla'crossroneof the control-'elec- :trodes ,and fthe cathode a voltage Yv'vhiich lis the 'algebraic :sum ofa fixed Voltage fand a YSvolta-ge directly proportionalto 'the current flowing be- -tween the cathode and both orfthe outputeleca -trodes, means for applying' across the `oth'eroi. the control electrodes and the! cathode a"voltage Which is the-algebraic sum cf f's'aiddirectlyproportional voltage and a 'voltage corresponding t'o the rate l"of ionization, a connection-from :the outputl electrode associated-With -said other of potential 'relative to a cathodeL and "anielectrode maintained at a .negative 'potential relative to the cathode and the current through one of the .electrodes is maintained constant by controlling the cathodeA emission, the current through the other electrode being representative of the pressure'inthe tube, in combination, amplifier means for amplifying a signal from the electrode through whichV the current is to be held constant, said amplier means including a pair of triodes having a com-mon cathode connection through a common resistance to a 'regulated potential, meansfior impressing regulated potentials on the plate and grid of one of said triodes so that both cathodes are held atV a fixed potential, Ymeans forimpressinga potential on the grid of the'other f said triodes proportional to the current through the electrode of the gauge tube'through which the current is to beheld constant, a cathode emission control for said gauge tube for'regulating the cathode femission'of said gauge 'Stube' in accordance Withfa Yvoltage signalappliedto the input of said Vemission control, 'and a con nection between the plate 'of said other triode and `.the `input of said emission control.

4. VIn an ion vacuum gauge wherein thegauge tube has an electrode maintained at a positive potential relative to a cathode'and anelect'rod'e maintained at a negative potential relative to the cathode and the current through one of the electrodes is maintained constant by controlling the cathode emission, the current through the'other electrode being representative rof the'pressure in the tube, in combination, an automatic control device in the vfilament circuit of said gauge-tube for regulating the la'ment current in accordance With a rvsignal voltage applied tothe input of said device, a pair ofy triodes having interconnected cathodes and avr common cathode resistance, a connection `from vsaid vcommon-'resistance to a fixed potential, respective connections through respective resistanoes from 'therespective platesof said tricdes to a common regulated plate voltage, a connection rfrom'the v grid of 'one of said triodes 'to' a. regulated gridvoltagea connection from .the grid of the other of said triodes to the' electrode of'said gauge tubethroug'h which the 'current isto be kept'constant, anda connection/from the'plate of said other Vof'said tri'odcs to the linput'of: said control device..

5. Inan ion vacuumgaugerwherein the gauge tube has anelectrode maintained lata positive .potential relative :to a cathode 'and an electrde maintained' at a Ynegative potential 'relative to the-cathode andthe `Icurrent'through onefoffthe electrodes'is maintained constant byicontrolling the 'cathode emission, the current 'through the other electrodebeing representative of the .prese gauge tubeV for regulating 'the vii'larnentcurrent Ymaccordan'ce 'with .a Signal VCH-,ageaphedftb the input of "saidfdevi'c'e, ai pair ofi triodeslhaving 'interconnected cathodes connected `to ground of said triodes through a resistance to ground, 10

and a connection from the plate of said other oi.' said triodes to the input of said control device.

HUGH G. NEIL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,334,143 Dushman v Mar. 16, 1920 1,592,364 Houskeeper July 13, 1926 1,649,016 Buckley Nov. 15, 1927 2,310,286

Hansel] Feb. 9, 1943 

